1. Field
Embodiments of the switching devices described herein relate to integrated circuit memories and, in particular, to the formation of non-volatile integrated circuit memories containing materials which exhibit a change in resistance.
2. Statement of the Problem
Non-volatile memories are a class of integrated circuits in which the memory cell or element does not lose its state after the power supplied to the device is turned off. Resistance switching memories are memories in which the active element is a material that changes its state between resistive and conducting states. Many different resistance switching memories have been proposed. See Stephan Lai, “Current Status of the Phase Change Memory and Its Future,” Intel Corporation, Research note RN2-05 (2005); U.S. Pat. No. 7,038,935 issued to Darrell Rinerson et al., on May 2, 2006; U.S. Pat. No. 6,903,361 issued to Terry L. Gilton on Jun. 7, 2005; U.S. Pat. No. 6,841,833 issued to Sheng Teng Hsu et al., on Jan. 11, 2005; U.S. Pat. No. 6,624,463 issued to Hyun-Tak Kim et al. on Sep. 23, 2003; B. J. Choi et al., “Resistive Switching Mechanisms of TiO2 Thin Films Grown By Atomic-Layer Deposition,” Journal of Applied Physics 98, 033715(2005); Jae-Wan Park et al., “Reproducible Resistive Switching In Nonstoichiometric Nickel Oxide Films Grown By RF Reactive Sputtering For Resistive Random Access Memory Applications,” J. Vac. Sci. Technol. A 23(5), September/October 2005; I. H. Inone et al., “Nonpolar Resistance Switching Of Metal/Binary-Transition-Metal Oxides/Metal Sandwiches Homogeneous/Inhomogeneous Transition of Current Distribution,” arXiv:Cond-mat/0702564 v.1 26, Feb. 2007; and U.S. Pat. No. 7,834,338 issued to S. Brad Herner on Nov. 16, 2010. None of these papers disclose a resistive switching element that is stable under normal voltage, currents, time, and temperatures at which non-volatile memories must operate.
A more stable memory is disclosed in U.S. Pat. No. 7,639,523 entitled “Stabilized Resistive Switching Memory” issued Dec. 29, 2009, to Jolanta Celinska, Mathew D. Brubaker, and Carlos A. Paz de Araujo; U.S. Pat. No. 7,872,900 entitled “Correlated Electron Memory” issued Jan. 18, 2011, to Carlos A. Paz de Araujo, Jolanta Celinska, and Mathew D. Brubaker; and U.S. Pat. No. 7,778,063 entitled “Non-Volatile Resistance Switching Memories And Methods Of Making Same” issued Aug. 17, 2010, to Mathew D. Brubaker Carlos A. Paz de Araujo, and Jolanta Celinska. The disclosures of the three foregoing patents, i.e., the U.S. Pat. No. 7,639,523, the U.S. Pat. No. 7,872,900 patent, and the U.S. Pat. No. 7,778,063 patent, are incorporated herein by reference to the same extent as though the patent disclosures were included identically herein. While these memories are stable, many examples of such memories use elements not normally used in complementary metal-oxide-semiconductor (CMOS) memories, such as platinum electrodes. Since many integrated circuit manufacturing facilities utilize CMOS manufacturing processes, it is more difficult to commercialize these memories. Further, commercial memory manufacturers many times have their preferred materials for electrodes, metallization, etc. Thus, it would be highly desirable to have a CeRAM non-volatile resistive switching memory and a process for making such a memory that was compatible with many different manufacturing processes, including CMOS technologies.